Vacuum sealable bags are popular for purposes of packaging and storing all types of objects and matter. Typically, vacuum sealable bags include two opposing sheets of plastic material, each sheet having an inner layer of heat-sealable material such as polyethylene, and an outer layer of a material resistant to gas permeation (known in the food storage bag and in other storage bag industries as “high barrier” material) such as nylon or polyester. The inner layer of vacuum sealable bags are often shaped to assist in evacuating such bags. For example, some vacuum-sealable bags having embossed or ribbed inner layers defining air channels extending to the mouth of the bag. These channels provide passages for air to exit the bag when placed under vacuum by a vacuum sealing apparatus. An increased thickness of the plastic sheets (e.g., the inner layer of a two-layer bag as described above) is often required to keep the channels open while the bag is under vacuum. An alternative is to use an intermediate reinforcing layer of plastic, such as a reinforcing layer between a heat sealable layer and a high barrier material layer (referred to above) of a two-layer bag.
Vacuum sealable bags are often sold in rolls. In many cases, the roll consists of a continuous tube of sheet material which is cut to a desired length and can be heat seal on an open end of the tube to form a bag.
Vacuum sealable bags that are shaped to better facilitate evacuation as described above are typically much more expensive than equivalent, non-vacuum sealable bags because of the increased material costs and special manufacturing processes needed to create such bags. As a result, the consumer may decide against purchasing vacuum sealable bags or abandon vacuum sealing altogether. Also, due to the increased thickness of the plastic material used in some conventional vacuum sealable bags that are heat-sealed, increased sealing times can be required to melt the heat sealable layers. Many conventional vacuum sealers utilize a heating wire with a fixed sealing time to melt the heat sealable layers. This fixed sealing time may not always be appropriate for different types of vacuum sealable bags. Insufficient sealing times may then lead to a leaking vacuum seal.
Fully evacuating the bags is also difficult to accomplish both with a conventional bag and a vacuum sealable bag. With a conventional bag, embossed or ribbed inner layers to provide air channels are non-existent. Typically, isolated pockets of trapped air are often left in the conventional bag upon sealing. This results when pockets of air no longer have an exit channel from the bag upon sealing. This is also a problem with some vacuum sealable bags. It is not uncommon for either embossed or ribbed walls of a vacuum sealable bag to collapse before complete evacuation has occurred, thereby trapping isolated pockets of air within the bag upon sealing.
In light of the problems and limitations of the prior art described above, a need exists for a vacuum-sealable bag apparatus and method in which improved storage bag evacuation is enabled, bags of different types can be evacuated, more reliable bag seals are produced, and the cost of vacuum sealing is reduced. Each preferred embodiment of the present invention achieves one or more of these results.